Internal combustion engines may be equipped with a turbocharged air induction system to improve the power output generated by the engine. The turbocharged air induction system increases engine power by forcing more air into the combustion chambers than would otherwise be possible. This increased amount of air allows for enhanced fueling that further increases the power output generated by the engine.
Turbochargers typically mount a turbine wheel and a compressor wheel onto a rotatable shaft. The shaft is typically rotationally supported within a housing by bearings that are lubricated by engine oil. Shaft seals are employed at both the compressor and turbine ends of the housing to prevent the high pressure gases from entering the housing (and then into the engine crankcase) as well as to prevent oil entering the compressor and turbine areas.
Even with shaft seals, under some conditions, oil can leak into the compressor area and get carried into the engine intake. To prevent or reduce the likelihood of oil leaking by the shaft seals, some manufacturers direct compressed air from the compressor to the seal area.
U.S. Pat. No. 6,368,077 to Meyerkord et al. (“the '077 patent”), for example, discloses a seal system from a four cycle engine turbocharger. The turbocharger includes a turbine wheel and a compressor wheel mounted on an oil-lubricated rotor shaft. Labyrinth seals at both the compressor and turbine end of the shaft are employed to limit oil leakage into the turbine area and the compressor area. In addition, air pressure from the output of the compressor wheel is conducted through internal passages in the bearing housing to the labyrinth seals to further prevent the passage of oil toward the compressor and turbine wheels.
Though the system in the '077 patent may help limit oil leaking into the compressor area, the multiple internal air passages add complexity to the system and the air pressure directed into the seals is unregulated and limited to the output pressure of the compressor.
The disclosed exhaust system is directed to overcoming one or more of the problems set forth above and/or other problems of the prior art.